Jam tolerant electromechanical actuation systems and methods of operation

ABSTRACT

In a vehicle, having a fixed supporting structure and a load movable relative thereto, a jam tolerant actuating system, a method for controlling this system including: Locating a physical coupling/decoupling mechanism between the load and an actuator assembly as close a practicable to the load; constructing the coupling/uncoupling mechanism to be reversible, and hence testable; and controlling the connection/disconnection via decision making electronics which will detect any system failure by monitoring, at a minimum: actuator main motor load and speed, and actuator output load. Also set forth are specific embodiments of pivotable rotary geared actuators as well as linear ball screw type actuators embodying the coupling/uncoupling mechanisms of this invention.

CROSS-REFERENCE TO RELATED CASES

The present application claims priority under 35 USC §120 to U.S. patentapplication Ser. No. 11/469,531 filed Sep. 1, 2006 which claims priorityunder 35 USC §120 to U.S. patent application Ser. No. 10/920,107 filedAug. 17, 2004 which claimed priority under 35 USC §119(e) to U.S.Provisional Application No. 60/511,506 filed Oct. 15, 2003. The entiredisclosures of these earlier applications are hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention pertains to jam tolerant electromechanicallyoperated actuation systems, of both the rotary and linear types,together with their methods of operation that can be universallyutilized wherever such actuation systems are required, e.g., invehicles, etc. Specifically, this invention pertains to electricaljam-detection systems and associated locking devices that can beelectrically engaged and disengaged that do not require an overload torelieve the jam and that are testable since the process is completelyreversible.

BACKGROUND OF THE INVENTION

One of the applications of the jam tolerant electromechanical actuationsystems of this invention, among others, is for the actuation of thinwing stabilizers (both vertical and horizontal), ailerons, canards,rudders for manned and unmanned aircraft, marine, submarine, spacecraft,as well as ground vehicles and the like. This invention makeselectromechanical actuators safer for primary flight control since iteliminates a mechanical jam potential in electromechanical actuators andthereby removes the last remaining technical obstacle that preventselectromechanical actuators from being used in primary flight controlapplications.

The patent literature includes a number of constructions that pertain tojam tolerant hinge line actuators, or other electromechanical actuators,that utilize frangible elements or other mechanisms to relieve a jamwhen an overload occurs. The patents listed below are merelyrepresentative of the prior art and are listed in chronological order asfollows: U.S. Pat. No. 3,958,779 to Townsend; U.S. Pat. No. 4,544,052 toBorden; U.S. Pat. No. 4,637,272 to Teske et al.; U.S. Pat. No. 4,885,939to Martin; U.S. Pat. No. 4,932,613 to Tiedeman et al.; U.S. Pat. No.4,979,700 to Tiedeman et al.; U.S. Pat. No. 5,071,397 to Grimm; U.S. PatNo. 5,518,466 to Tiedeman; U.S. Pat. No. 5,779,587 to Reilly; U.S. Pat.No. 5,947,246 to Koller; U.S. Pat. No. 6,231,012 B1 to Cacciola et al.;U.S. Pat. No. 6,260,799 B1 to Russ; U.S. Pat. No. 6,443,034 B1 toCapewell et al.; and U.S. Pat. No. 6,705,570 to Degenholtz et al.Several of these constructions will be discussed in more detail asfollows:

Turning first to U.S. Pat. No. 3,958,779 to Townsed, pertains to jamtolerant surface control but not to a hinge line actuator. U.S. Pat. No.4,932,613 to Tiedeman et al. incorporates a two slice hinge planetarymechanism which uses helical gearing to provide greater torque outputfor a given volume. The helix angles are opposite between left and rightslices such that the thrust loads generated on these gears will acttowards each other and ultimately cancel each other out. Thus there doesnot need to be any additional structure to carry the thrust loads. Thestructures of the present invention do not utilized opposing helicalgears. U.S. Pat. No. 5,518,466 to Tiedeman achieves jam tolerancethrough the use of frangible elements at both the input and output ofthe hinge. Thus, a jammed hinge can be severed from the surface,allowing same to be driven by the remaining gear boxes, and the motorcan be severed if a single motor is driving multiple gearboxes. None ofthe embodiments of the present invention use frangible elements.

U.S. Pat. No. 4,544,052 to Borden pertains to a coupling, rather than anactuator, that can be electrically disconnected, but must be manuallyreconnected. It entails the use of heavy compression springs todisconnect the load wherein these springs are released by electricallyactivating a small solenoid, allowing same to be disconnected quickly.Furthermore, this structure cannot be reconnected while the system isloaded or in motion. The design of the present invention permits bothelectrical connection and disconnection, both of which are achievablewhile the system is loaded and/or moving.

Continuing with U.S. Pat. No. 5,071,397 to Grimm, this design, similarto one of the embodiments of the present invention, also uses a hingeline planetary arrangement. However, the Grimm design has thedisconnection occurring at the input shaft portion of the hinge lineplanetary. This feature does not allow the system to continue operatingafter a failure. The designs of the present invention use multipleactuators on a single surface. Thus, when one actuator fails (jammed orotherwise) it is removed from the system by disconnecting same andcontinuing operation with the remaining healthy actuator(s). If a jamoccurred in the Grimm gear train, e.g., at the planet gear (item 2 inFIG. 1 thereof), while the input shaft would not be jammed, the outputwould be undesirably fixed in place. In the constructions of the presentinvention, the disconnection occurs at the point where the actuatorcouples to the load so that any jam anywhere in the actuator can bedisconnected. In addition, in this Grimm device, the disconnectingmechanism is triggered automatically by an overload and will resetitself automatically when the overload is removed. The present inventionuses electronics and software to continually monitor the system andevaluate same for unacceptable performance which may not necessarilymanifest itself in an overload. When the decision is made to remove theactuator from the system, it is fully removed and cannot be re-engageduntil commanded to (the system being stable in both the engaged anddisengaged positions).

Turning now to U.S. Pat. No. 5,779,857 to Reilly, this design, similarto that of the present invention, disconnects at the actuator output.However, the Reilly disconnection is triggered by an overload of theinput shaft. As already noted, an actuator failure may not alwaysmanifest itself as an overload and thus the Reilly design would not betolerant of other types of failure. It should also be noted that eventhough the load is disconnected at the output, the overload sensing isat the input. Thus, if a failure occurred while the system was supposedto be dormant and holding a steady load, it would not disconnect ifsubjected to an excessive back driving load from the output. Onlyforward driving torque can activate the Reilly system. In addition, anddiffering from the structures of the present invention, it uses afrangible element to achieve the “jam-tolerant” mode. Frangible elementscannot be tested prior to use.

None of the noted prior art constructions utilize reversibledisengagement without human intervention (testable on the vehicle) andthe disengagement of the actuator from the load at or as close as ispracticable to the output (closest to load). In addition, in theembodiments of the present invention, actuator fault (any type offailure or degradation is determined by monitoring, at a minimum, motorspeed, motor load, and output load (with “motor” including any source ofmechanical or hand power) and activating the electronically controlleddisengagement mode.

SUMMARY OF THE INVENTION

Accordingly, in order to overcome the deficiencies of the prior artdevices, the several embodiments of the present invention not onlyprovide jam tolerant electromechanical actuating systems that permitphysical disconnection between the load and the actuator as close aspracticable to the load, but also permit the disconnection to bereversible and hence testable, with the disconnection being controlledby decision-making electronics which will detect any failure bymonitoring, at a minimum of: main motor load, main motor speed andoutput load.

Specifically, in an aircraft, having a fixed supporting structure and acontrol surface movable relative thereto, a jam tolerant actuatingsystem including a computer, control means and at least twoelectromechanical actuator assemblies, each of the actuator assembliesfurther including a main motor for providing motion force therefore; aload sensor and a position sensor on the actuator assembly; acoupling/decoupling mechanism, positioned at the output member of theactuator assembly, for severing the load path between the actuatorassembly and the movable surface; and a disconnect actuator forproviding motive force for the coupling/decoupling mechanism, a methodfor controlling the actuating system, comprising the steps of: operatingthe movable control surface by the actuator assembly via the main motor,as directed by the computer via Command and Power inputs through thecontrol means; relaying, from the control means to the computer, aplurality of the following inputs; i. main motor speed from a main motorcommutator; ii. main motor current; iii. actuator assembly output loadfrom the load sensor; and iv. actuator assembly output position,processed to determine speed, from the position sensor; and completelysevering, via decoupling, the load path between the actuator assemblyand the movable surface, via driving the coupling/decoupling mechanismin one direction, upon the detection of a malfunction, as determined bythe control means, based on at least three of the above i., ii., iii.,and iv. inputs.

One variation thereof includes the further step of reversing theprevious decoupling step, at any time, thereby reestablishing the loadpath, between the actuator assembly and the movable control surface, bydriving the coupling/decoupling mechanism in a reverse direction.Another variation thereof further includes the steps of: indirectlymeasuring, via the load sensor, the load present or occurring at theoutput member of the actuator assembly; indirectly measuring, theactuator assembly input load; and comparing the input and output loadsto detect if a jam or other type of failure has occurred within theactuator assembly or the control system.

In the above methods for controlling, the comparing of input and outputloads may be limited to one of the actuating assemblies or used inconjunction with similar readings from additional, redundant, actuatorassemblies.

In the previously-noted methods for controlling, the actuator assembliesmay include rotary actuators, specifically geared rotary actuators, witheach of the actuators including a compound planetary gear set, wherein acentral internal ring gear, having laterally-spaced first edgeengagement members, is operatively interconnected, in one operatingposition, to an output member attached to the movable surface, vialaterally-spaced and laterally movable opposed lock plates, the lockplates having laterally-spaced second edge engagement members andradially-extending pins, the second edge engagement members, in oneoperative position, being adapted to operatively interact with theirrespective first edge engagement members; an engagement/disengagementcollar having a plurality of peripheral cam slots, with the pinsentering the cam slots; a sector gear located on a peripheral portion ofthe collar, the sector gear being in operative engagement with thedisconnect actuator, the latter, depending upon the direction ofrotation, coupling/uncoupling the output member with the rotary gearedactuator via rotation of the collar, which in turn results, via movementof the pins, in the lateral movement of the lock plates and in one ofthe engagement and disengagement of the first and second engagementmembers.

In the noted method for controlling the actuator assemblies may alsoinclude linear actuators, specifically linear actuators of the ballscrew type, with each of the actuators including a bidirectionallyrotatable power driven ball screw; a reciprocable ball nut havingperipherally-spaced outward first surface engagement portions, driven bythe ball screw, the ball nut being operatively interconnected in oneoperating position, to an output member attached to the movable surface,via laterally adjacent and oppositely rotationally movable front andrear locking plates, the locking plates having respectiveperipherally-spaced inward second surface engagement portions andrespective radially extending sector gear portions, the second surfaceengagement portions, in one operative position, being adapted tooperatively interact with the first surface engagement portions; thesector gear portions being in operative engagement with opposite sidesof a face gear of the disconnect actuator, the latter, depending uponthe direction of rotation, coupling/uncoupling the output member withthe ball screw actuator via rotation of the sector gear portions, whichin turn results, via movement of the sector gears, in the peripheralmovement of the locking plates and in one of the engagement anddisengagement of the first and second engagement portions.

In one of the methods for controlling of this invention, the controlsurface is one of a primary and secondary control surface of theaircraft.

In a further variation of this invention, in a vehicle, having a fixedsupporting structure and a load movable relative thereto, a jam tolerantactuating system includes the following operatively interconnectedcomponents: a computer, an electronic decision-making controller and atleast two actuator assemblies, each of the actuator assemblies furtherincluding a main mechanical power source for providing motion forcetherefore; a load sensor and a position sensor on the actuator assembly;a coupling/decoupling mechanism, positioned at the output member of theactuator assembly, for completing/severing the load path between theactuator assembly and the load; and a disconnect mechanical power sourcefor providing motive force for the coupling/decoupling mechanism, amethod of controlling the jam-tolerant actuating system, comprising thesteps of: a. actuating the load via the actuator assembly as directed bythe computer via Command and Power inputs through the controller; b.relaying, from the controller to the computer, at least three of thefollowing inputs: i. speed of the main mechanical power source; ii. mainmechanical power source load; iii. actuator assembly output load fromthe load sensor; and iv. actuator assembly output position, processed todetermine speed, from the position sensor; and c. decoupling, viacompletely severing, the load path between the actuator assembly and theload, via driving the coupling/decoupling mechanism in one direction,upon the detection of a malfunction, as determined by the controller,based on multiples of the inputs from step b.

In a variation of the previous method, the method of controlling furtherincludes the step of: reversing the previous decoupling step, at anytime, thereby reestablishing the load path, between the actuatorassembly and the load, by driving the coupling/decoupling mechanism in adirection opposite to the one direction. This variation can also includethe steps of: measuring, via the load sensor, one of the load presentand occurring at an output member of the actuator assembly; measuringthe actuator assembly input load; and comparing the input and outputloads to detect if one of a jam and other type of failure has occurredwithin one of the actuator assembly and the control system. In addition,in these methods of controlling, the comparing of input and output loadsmay be limited to the input and output loads of the same actuatingassembly or used in conjunction with similar readings from additional,redundant actuator assemblies.

In the previous method of controlling the actuator assemblies arecomprised of one of rotary actuators, preferably electromechanicalgeared rotary actuators, or of linear actuators, preferably ofelectromechanical ball screw-type actuators.

In another embodiment of this invention, in a vehicle having a fixedsupporting structure and a load movable relative thereto, a jam tolerantactuating system includes the following operatively interconnectedcomponents: a computer; an electronic decision-making controller; and atleast two rotary geared actuator assemblies, each of the actuatorassemblies further including a main mechanical power source forproviding motion force therefore; a load sensor and a position sensor onthe actuator assembly; a coupling/uncoupling mechanism, positioned atthe output member of the actuator assembly, for completing/severing theload path between the actuator assembly and the load; and a disconnectmechanical power source for providing motive force for thecoupling/decoupling mechanism, the rotary geared actuator assemblyfurther including: a compound planetary gear set, wherein a central ringgear, having opposing, laterally-spaced, first edge engagement members,is operatively interconnected, in one operating position, to the outputmember attached to the movable load; via laterally-spaced and laterallymovable opposed lock plates, the lock plates having laterally-spacedsecond edge engagement members and radially extending pins, the secondedge engagement members, in one operative position, being adapted tooperatively interact with respective adjacent ones of the firstengagement members; an engagement/disengagement collar having aplurality of peripherally extending cam slots, with the pins enteringthe cam slots; and a sector gear located on a peripheral portion of thecollar, the sector gear being in operative engagement with thedisconnect mechanical power source, the latter, depending upon thedirection of movement, coupling/uncoupling the output member with therotary geared actuator assembly via rotation of the collar, which inturn, via movement of the pins, in the lateral movement of the lockplates and in one of the engagement and disengagement of the first andsecond engagement members.

In the jam tolerant actuating system of the preceding embodiment, aprocess of controlling the system, includes the following steps: a.actuating the load via the actuator assembly as directed by the decisionmaking controller via Command and Power inputs from and Status inputs tothe computer; b. relaying, from the controller to the computer, at leastthree of the following inputs: i. speed of the main mechanical powersource; ii. main mechanical power source load; iii. actuator assemblyoutput load from the load sensor; and iv. actuator assembly outputposition, processed to determine speed, from the position sensor; and c.decoupling, via completely severing, the load path between the actuatorassembly and the load, as determined by the controller, based on theinputs of step b. This process of controlling may further include thestep of d. reversing, at any time, the previous decoupling of step c,thereby reestablishing the load path, between the actuator assembly andthe load, by driving the coupling/uncoupling mechanism in a directionopposite to the one direction.

In a further embodiment of this invention, in a vehicle, having a fixedsupporting structure and a load movable relative thereto, a jam-tolerantactuating system includes the following operatively interconnectedcomponents: a computer; an electronic decision-making controller and atleast two linear actuator assemblies, each of the actuator assembliesfurther including a main mechanical power source for providing motionforce therefore; a load sensor and a position sensor on the actuatorassembly; a coupling/decoupling mechanism, positioned at the outputmember of the actuator assembly, for completing/severing the load pathbetween the actuator assembly and the load; and a disconnect mechanicalpower source for providing motive force for the coupling/decouplingmechanism, the linear actuating assembly further including: a. abidirectionally rotatable power driven ball screw; b. a reciprocableball nut, actuated via the ball screw, having peripherally-spacedoutward first surface engagement portions, the ball nut beingoperatively interconnected in one operative position, to the outputmember attached to the movable load, via c. laterally adjacent andoppositely rotationally movable front and rear locking plates, thelocking plates having respective peripherally-spaced inward secondsurface engagement portions and respective radially extending sectorgear portions, the second surface engagement portions, in one operativeposition, being adapted to operatively interact with the first surfaceengagement portions, the sector gear portions being in operativeengagement with d. opposite sides of a face gear of the disconnectmechanical power source, the latter, depending upon the direction ofmovement, coupling/uncoupling the output member with the linearactuating assembly via opposite rotation of the sector gear portions,which in turn, results, via movement of the sector gears, in theperipheral movement of the locking plates and in one of the engagementand disengagement of the first and second engagement portions.

In the jam tolerant actuating system of this embodiment, a process ofcontrolling the system includes the following steps: a. actuating theload via the linear actuator assembly as directed by the decision makingcontroller via Command and Power inputs from and Status inputs to thecomputer; b. relaying, from the controller to the computer, at leastthree of the following inputs: i. speed of the main mechanical powersource; ii. main mechanical power source load; iii. actuator assemblyoutput load from the load sensor; and iv. actuator assembly outputposition, processed to determine speed, from the position sensor; and c.decoupling, via completely severing, the load path between the actuatorassembly and the load, via driving the coupling/uncoupling mechanism inone direction, upon the detection of a malfunction, as determined by thecontroller, based on the inputs from step b. This process of controllingpreferably includes the steps of: measuring, via the load sensor, theload present at the output member; measuring the actuator assembly inputload; and comparing the input and output loads to detect if a jam hasoccurred.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a first embodiment of theelectromechanical actuators according to the present invention.

FIG. 2 is a top plan view of the actuator of FIG. 1.

FIG. 3 is a side plan view of the actuator of FIG. 1.

FIG. 4 is a sectional view, taken along line 4-4 of FIG. 3.

FIG. 5 is an enlarged longitudinal sectional view, taken along line 5-5of FIG. 2.

FIG. 6 is an end view, partially in section, of the RVDT-end of theactuator of FIG. 3 looking in the direction of arrows 6-6 of FIG. 3.

FIG. 7 is a sectional view, partially broken away, taken along line 7-7of FIG. 6.

FIG. 8 is a sectional view, partially broken away, taken along line 8-8of FIG. 4.

FIG. 9 is a view, similar to that of FIG. 2, with parts removed, showingthe actuator in a disengaged position.

FIG. 10 is a view, similar to that of FIG. 9, with further partsremoved.

FIG. 11 is a view, similar to that of FIG. 1, with parts removed,showing the actuator in the disengaged position.

FIG. 12 is an enlargement of circled area 12 of FIG. 11, showing detailsof the disengagement.

FIG. 13 is a view, similar to that of FIG. 9, but showing the actuatorin an engaged position.

FIG. 14 is a view, similar to that of FIG. 10, but showing the actuatorin an engaged position.

FIG. 15 is a view, similar to that of FIG. 11, but showing the actuatorin the engaged position.

FIG. 16 is an enlargement of circled area 16 of FIG. 15, showing detailsof the engaged position.

FIG. 17 is an enlarged view, with parts removed for the sake of clarity,looking in the direction of arrows 17-17 of FIG. 1, showing the majorrotating parts of the compound planetary gearing of this actuator.

FIG. 18 is a schematic illustration of a first jam tolerantelectromechanical actuation system that utilizes the actuator of FIG. 1.

FIG. 19 is a perspective schematic view of a portion of a secondembodiment of the electromechanical actuators according to the presentinvention.

FIG. 20 is a view, similar to that of FIG. 19, without the mode motorand gearbox of the latter.

FIG. 21 a is an enlarged perspective schematic view of the unique ballnut and the ball screw that are utilized in FIGS. 19 and 20.

FIG. 21 b is a view, similar to that of FIG. 21 a including one of thetwo locking plates associated therewith.

FIG. 22 is a view, similar to that of FIG. 21 b including both of thelocking plates.

FIG. 23 is a view, similar to that of FIG. 22 including the severalthrust bearings associated with the locking plates.

FIG. 24 a is a schematic bottom view of the actuator of FIG. 19, shownin an uncoupled position.

FIG. 24 b is a view, similar to that of FIG. 24 a, but shown in acoupled position.

FIG. 25 a is an end view, of the mode motor and gear box end of FIG. 24a.

FIG. 25 b is an end view, of the mode motor and gear box end of FIG. 24b.

FIG. 26 a is a longitudinal side view of the actuator of FIG. 24 a.

FIG. 26 b is a longitudinal side view of the actuator of FIG. 24 b.

FIG. 27 a is an enlarged longitudinal sectional view, taken along line27 a-27 a of FIG. 24 a.

FIG. 27 b is an enlarged longitudinal sectional view, taken along line27 b-27 b of FIG. 24 b.

FIG. 28 a is a lateral sectional view, taken along line 28 a-28 a ofFIG. 27 a.

FIG. 28 b is a lateral sectional view, taken along line 28 b-28 b ofFIG. 27 b.

FIG. 29 a is a further lateral sectional view, taken along line 29 a-29a of FIG. 28 a.

FIG. 29 b is a further lateral sectional view, taken along line 29 b-29b of FIG. 28 b.

FIG. 30 is a schematic illustration of a second jam tolerantelectromechanical actuation system that utilizes the actuator of FIG.19.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein like numerals are used throughoutthe several views to designate like parts, and more particularly toFIGS. 1, 2, 3 and 18, illustrated therein is an electromechanical gearedrotary actuator (GRA), generally designated by reference numeral 22,suitable for use, for example, in single and/or multiple jam-resistantelectromechanical actuating systems, such as single unit actuator system20, shown in FIG. 18. GRA 22, which is utilized, for example, forprimary or secondary flight surface control, includes, as best seen inFIGS. 1 and 18, an input power source, such as a bidirectionallyrotatable prime mover or mechanical power source, such as electric motor24, the proximate end of which is fixedly secured, via a plurality ofbolts 28, to a connector housing 26, which in turn is connected, via aplurality of further bolts 32, to grounded housing structures 30 a, 30b, that include axially-spaced, separate, front and rear end flangeportions 36 and 38, respectively, all of which will be described in moredetail hereinafter. Again as best illustrated in FIGS. 1 and 18, an edgesurface of flange portion 38 is provided with an affixed load sensor 34,preferably in the form of a strain gauge of any desirable commerciallyavailable type.

Located intermediate stationary flange portions 36, 38 is a rotatable orpivotable output structure 40 which functions to provide a mechanicalconnection to the load, i.e., the surface that needs to be controlled,with output structure 40 including an output flange portion 42, all ofwhich will again be described in more detail hereinafter. The front endof GRA 22, extending axially beyond front end flange portion 36, isclosed via a front hinge cover 46 that is secured to flange portion 36via a plurality of bolts 48. As best seen in FIG. 1, a commerciallyavailable reversible or bidirectional rotary electric motor 24, whichfor the sake of electrical redundancy is shown here, for example, as atandem dual motor assembly, includes dual circumferentially-spacedreceptacles 50 a, 50 b (FIG. 2), located on the periphery of connectorhousing 26, that function for electrical connections to the dual motorwindings, respectively, while a further receptacle 52, intermediatereceptacles 50 a, 50 b, functions for electrical connections for thedual motor resolvers and commutators for logic/motor position controland/or sensing in a manner well known in the art.

Turning now additionally to FIGS. 4 and 5, which are transverse andlongitudinal sectional views, respectively of GRA 22, rotational powerfrom motor 24 is coupled (not shown per se) to an intermediate shaft 56,which has a sun gear 60, fixedly attached to the distal end thereof,with sun gear 60 functioning as an input member. Sun gear 60, in turn,is in meshed relationship with at least one planet gear 62 which alsomeshes with and reacts against a fixed internal ring gear 66 that isaffixed to an end face of grounded housing structure 30 a. A rotatableplanet carrier 64 thus acts as the output member. This combination ofintermeshing gears 60, 62, 66 and planet carrier 64, together comprise asupplementary or optional gearing speed reducer structure 70 that may ormay not be required, depending upon the type and severity of service ormoving force required of GRA 22.

A central hub portion 72 of output planet carrier 64 is splined to theproximate end of a central, longitudinally-extending, preferably hollowinput shaft 74, journalled in carrier 64 on its proximate end, may ormay not extend completely through GRA 22 and is journalled, in thisembodiment, on its distal end, in front hinge cover 46. Input shaft 74,at its about longitudinal center portion, includes a preferably integralhinge sun gear 76, forming a part of a hinge assembly planetary geartrain 44, which meshes with the center portions or segments of aplurality of preferably hollow hinge planet gears 78 that includeintegral, axially-spaced, planet outer portions 78 a, 78 b, and planetcenter portions 78 c. Planet outer portions 78 a, 78 b, arelongitudinally as well as radially spaced and separated about hinge sungear 76 via longitudinally separated ring spacers 80.

Grounded housing structures 30 a, 30 b, in addition to their separateflange portions 36, 38, also include respective cylindrical portions 84a, 84 b, each having stepped peripheral surfaces 86 as well asrespective fixed, peripheral outer ring gear portions 88 a, 88 b thatare also in respective meshing relationship with hinge planet gearportions 78 a, 78 b. Thus, it should be understood that hinge planetgear portions 78 a, 78 b, revolve around hinge sun gear 76, withperipheral outer ring gear portions 88 a, 88 b, serving as reactionmembers. Portions of this gear train are also illustrated in FIG. 8 andparticularly in FIG. 17.

The center portions 78 c of planet hinge gear 78, in addition to meshingwith sun gear 76, also mesh with a rotatable, central internal ring gear92, axially interposed between, but spaced from fixed ring gear portions88 a, 88 b. It is the differential ratio between the outer internal ringgears 88 a, 88 b,/outer planet gear portions 78 a, 78 b, and the centerring gear portion 92/center hinge planet gear portions 78 c, thatproduce the motion of central internal ring gear 92 relative to theouter internal ring gear portions 88 a, 88 b. It should be understoodthat the previously-described hinge motion, achieved via planetary geartrain 44, could also be achieved via other forms of power transmissionswell known in the art.

Continuing with the FIGS. 4 and 5 descriptions, acylindrically-extending portion 94 of output flange portion 42 ofpivotable output structure 40, is rotatably journalled, viaaxially-spaced rolling element bearings 96 retained on spaced steppedperipheral surfaces 86 of housing structures 30 a, 30 b. Thus, it shouldbe understood that cylindrical portion 94, connected to the load,together with output flange portion 42, can rotate or pivot relative togrounded housing structures 30 a, 30 b. In order to minimize any axialmovement of cylindrical portion 94, relative to the radial outer surface98 of central internal ring gear 92, while still permitting rotarymovement thereof, the former is linked relative to the latter via aninternal lock ring 100.

Turning now additionally to FIGS. 11, 12, 15 and 16, also slidablylocated on opposed, stepped peripheral housing surfaces 86 areoppositely-directed, generally annular, lock plates 104 a, 104 b, eachhaving a plurality of laterally inwardly-extending tooth portions 106that are capable of meshing with corresponding lateral tooth portions108 extending from opposed ends of the surface 110 of the body ofinternal ring gear 92 of actuator 22. Lock plates 104 a, 104 b, serve tocouple and uncouple element portions 94 and 110. The interaction oftooth portions 106-108 is best shown, in this disengaged position inFIGS. 11 and 12, and in their engaged position in FIGS. 5, 15 and 16. Asbest seen in FIG. 17, output cylindrical portion 94 is also providedwith opposed laterally extending tooth members 114 which are designed tocorrespond with tooth members 106 and 108. In summary, power istransferred from internal ring gear 92, through opposed teeth 108, tothe mating teeth 106 on the radially innermost portions of lock plates104 a, 104 b, then through the radially outermost portions of lock plateteeth 106, and finally into tooth members 114 on output member 94.

Lock plates 104 a, 104 b, are further provided with pluralities ofcircumferentially-spaced, laterally outwardly-directed dowel pins 116,each of which extends fully through laterally elongated apertures 118(FIGS. 10, 11) in output cylindrical portion 94 as well as at leastextending into an individual skewed slot 122 (FIGS. 9, 14) in aperipheral, cylindrical, lock collar 120 extending around, and rotatablymoveable, relative to, the outer peripheral surface of output portion94. A peripheral portion of lock collar 120 is provided with a sectorgear 124 (FIGS. 8, 9, and 13) of limited circumferential extent,preferably in the range of 15 to 45 degrees. As will be explained indetail later, sector gear 124 is adapted to be engaged with andreversibly driven by a spur gear train assembly 126 (FIGS. 5, 8),thereby rotating lock collar 120 relative to output portion 94. Lockcollar 120 is enclosed within a further multi-shape peripheral outerhousing 130 whose inner axial end portion abuts output flange portion 42and its outer axial end portion abuts at an intermediate cover 132,interposed between outer housing 130 and front hinge cover 46. As bestseen in FIGS. 1-3, outer housing 130 is secured, on one axial end, tooutput flange portion 42 and, on its other axial end, to intermediatecover 132 via a plurality of bolts 134. It should be understood at thistime, particularly with reference to FIGS. 1 and 2, that pivotableoutput structure 40, including outer housing 130, intermediate cover 132and flange portion 42, can move peripherally relative to groundedhousing structures 30 a, 30 b, including their respective flangeportions 38, 36. This is graphically illustrated in FIG. 2 wherein thesections G1 and G2 that remain stationary to ground are shown confinedwithin broken lines, while the section R that rotates with the load,around rotational axis 136, is shown confined within the dotted lines.

As possibly best seen in FIGS. 5 and 8, located within a cavity definedby outer housing 130 and intermediate cover 132, is spur gear trainassembly 126, of a decoupling mechanism 128, which can be reversiblyrotated by an external driving source or actuator, such as electricconnect/disconnect motor 138. The exact structural details of the gearreduction sequence of gear train assembly 126 are not critical and arereadily deducible by one of ordinary skill in the art. What is importantis that a cluster gear 140 meshes with and drives sector gear 124 ofcylindrical lock collar 120, and that a torque limiting clutch 142, ofany desired conventional construction, functions to prevent possibleoverload damage to gear train assembly 126. It should, of course, beclear to those skilled in the art, that other embodiments of jamtolerance mechanisms may not require or need the use of a torquelimiting clutch, such as 142.

Turning now to FIGS. 3, 5, 7 and 8, intermediate cover 132 includes acurved sector housing portion 144 that extends sectorially (not shownper se) for a predetermined angular range (of about 45 to 120 degrees,for example) around but not in contact with, a portion of groundedhousing structure portion 30 b and contains therein a curved sector gear146 of about the same angular extent. Sector gear 146 operativelyinteracts with a gear portion of a commercially available rotaryvariable differential transformer (RVDT) 150 that is located within ahousing portion 152 of front hinge cover 46 and closed via its own cover154. It is the function of RVDT 150 to serve as a position sensor,specifically of rotational angles, in a manner well known in the art,for determining the angular location or position of pivotable outputstructure 40, relative to grounded housing structure 30 b, for controlpurposes to be described in detail, later. As is well known in the art,RVDTs utilize rotary ferromagnetic cores and are capable of continuousrotational measurement. Again, the exact structural details of RVDT 150are not critical and are easily deducible by one of ordinary skill inthe art. What is important is the determination of the angular locationof the pivotable output structure relative to the grounded housingstructure, which in addition to using an RVDT, could also beaccomplished by other position sensors such as, e.g., potentiometers,resolvers and syncros. In addition, such a position sensor could also beincorporated into the overall system, without being physically attachedto the actuator, i.e., it could be mounted directly between the vehiclestructure and the surface or item it senses as a separate physical unitthat is electrically connected to the system.

Turning now to the operation of GRA 22, FIGS. 1, 5 and 15, 16 illustratesame in the normal operation thereof, i.e., when pivotable outputstructure 40 is mechanically coupled to grounded housing structure 30 a,30 b, via the previously-noted intermeshing of tooth portions 106-108and 114. Thus, in the coupled or engaged stage/state, main motor 24,affixed to grounded housing portions 30 a, 30 b, acting through optionalgearing speed reducer 70, if required, and planetary gear train 44,transfers the motor rotary motion or torque to pivotable/rotatableoutput flange portion 42 which in turn is mechanically interconnected(not shown) to the load, i.e., the previously-noted movable surface thatis controlled therewith. It is important to understand, at this time,that this invention contemplates that each such movable surface, for thesake of redundancy, is controlled via independent multiples of GRAs 22.

During such normal operational phases, bidirectional main motor 24operates to pivot the noted movable surfaces, as directed, asillustrated in FIG. 18, by a vehicle computer 160, acting via Commandand Power inputs, through an electronic controller 162, which in turncontrols the function of main motor 24 and, as will be discussed later,also controls the function of disconnect motor 138. A Status inputrelays required information from controller 162 back to vehicle computer160, with controller 162 receiving at least some of the following inputsfrom GRA 22:

Main Motor Speed from commutator 52;

Main Motor Current from main motor 24;

GRA Output Load (preferably determined by strain)from load sensor 34;and

GRA Output Position (processed, such as by differentiation to determinespeed) from position sensor (RVDT) 150.

Upon the detection of a malfunction, such as, for example of a jam orother failure, of GRA 22, as determined by electronic controller 162,based on one or more of the just noted GRA inputs, decoupling mechanism128 serves to completely sever the load path between GRA 22 and theload. Specifically, decoupling mechanism 128 includes thepreviously-recited spur gear train assembly 126, driven byreversible/bidirectional disconnect motor 138, whose cluster gear 140meshes with and drives sector gear 124 of cylindrical lock collar 120.Rotational movement of lock collar 120, in one direction, causesmultiple dowel pins 116, extending radially outwardly from opposed lockplates 104 a, 104 b, and extending through laterally-elongated apertures118, in cylindrical portion 94, as well as extending into theindividual, skewed, peripheral slots 122 (in lock collar 120), to beaxially displaced and thereby driving lock plates 104 a, 104 b, out ofengagement with the opposed mating portions of cylindrical portion 94and the mating side portions of central internal ring gear 92, resultingin the complete disengagement of the intermeshing of tooth portions106-108 and 114. It is a first important feature of this invention thatthe above decoupling method or process can, of course, also be reversed,at any time, (by driving disconnect motor 138 in a reverse or connectdirection) to thereby re-couple the load to GRA 22.

In addition, a second important feature of this invention is that GRA 22is provided with sensing device or strain gage 34 to sense or measure,either directly or indirectly, the load present or occurring at outputmember or structure 42. The system control, as illustrated in FIG. 18,can then compare the input load (either by direct or indirectmeasurement, such as via main motor current, and the like) to the outputload, as well as the input speed and the output speed (using positionand/or velocity sensors at main motor 24 and the load). This comparison,either by itself or used in conjunction with readings from additionalredundant GRA(s) can be used to detect if a jam or other type of failurehas occurred within GRA 22 or its control.

The above-recited two features, namely the load and speed comparisons,allow system 20 to detect a jam or other failure and isolate same fromthe remainder of the system 20 by activating the decoupling mechanism inthe failed GRA unit 22. When used in a multiple GRA configuration, afailed GRA 22 can be effectively removed from system 20 withoutdetriment to the remaining operative or healthy GRAs. It should beunderstood that a single computer 160, together with a single controller162, can be utilized to control and monitor multiple GRAs 22. Thisremoval of a failed GRA 22 will permit continued overall system functionwith full rate capability and load capability, reduced by one GRA overthe total number of GRAs being utilized. The system is designed toproduce a certain amount of load at a certain speed. The load that thesystem produces is the sum of the loads from each GRA. Upon the failureof one GRA, the load that the system can produce is reduced, but thespeed at which it can move the load is unaffected. In the event of afailure, if but a single GRA 20 is remaining in the system, theelectronic controller 162, in conjunction with the vehicle computer 160,may instruct GRA 20 to transition the load to a fixed neutral location.It should be understood that when using these GRAs, a system can neveremploy but a single actuator since the ability to tolerate a jam dependson having another GRA, other than the jammed one, to carry on therequired operations. It should also be clear that it is the decision ofthose in charge of the vehicle computers as to whether to continueoperation when only a single operative actuator remains or whether torevert to a safe mode and hold the item being controlled at a fixed,safe position.

In addition to the previously noted failure detection and isolationcapability of system 20, system 20 has an additional feature in that itis also able to monitor trends in the relationship between GRA inputpower and output power as a part of a prognostic health or operationalmonitoring regime. This additional feature thus imparts the ability todetect certain impending failures before they actually occur and providean alert signal to service the about-to-be impaired GRA prior tocomplete failure. The development of equipment health monitoringalgorithms is still underway and testing thereof will be required beforethere can be quantitative characterization of actuator degradation, butupon the completion of this development, the systems of this inventionare deemed to be capable of providing all of the information necessaryfor these systems to detect imminent faults.

The approach, in the method or process of the present invention, namelyof severing the mechanical link of a power transmission device, at theload, while utilizing a completely reversible method or process isunique. This allows the decoupling mechanism 128 to potentially betested prior to each use to eliminate the possibility of latentfailures. The ability of the method or process of the system of thisinvention to actively control the decoupling also allows for GRA unit 22to be decoupled for reasons other than mechanical overload. If a failurein system 20, that causes GRA unit 22 to decouple is determined tooriginate outside of unit 22, unit 22 can be re-coupled an re-usedwithout the need for removal, refurbishment, or maintenance.

The method/process of the present invention may best be described in thesystem's employment of the features or characteristics as follows:First, reversible disengagement, without human intervention, (testableon the vehicle) and the disengagement of GRA 22 from the load at or asclose as is practicable to the output (closest to load). Second,actuator fault (any type of failure or degradation) is determined bymonitoring, at a minimum, main motor speed, main motor load, and outputload. It should be understood that “motor” is deemed to refer to anysource of mechanical power, i.e., electric motor, hydraulic motor, handcrank, etc., with this monitoring then activating the electronicallycontrolled disengagement of the power transmission device, at the load.Furthermore, the method/process of system 20 is intended to cover allembodiments involving electronically controlled reversible disengagingload paths for mechanical power actuation.

Turning now to FIGS. 19-30, illustrated therein is a portion of a secondembodiment of the present invention, namely a linear actuator, generallydesignated by reference numeral 222. Parts thereof that are similar oranalogous to those of the first embodiment or GRA 22 are identified witha double prime (″) suffix. Linear actuator 222 is electromechanicallydriven by a conventional ball screw 224, best shown in FIGS. 27 a, 27 b,and a unique, special ball nut 226. Linear actuator 222 is suitable foruse, for example, in single and/or multiple jam-resistantelectromechanical actuating systems, such as the actuator system 220shown in FIG. 30. Once again, it should be understood that jam tolerancecannot be achieved with only one actuator and the more actuators thereare in a system, the more jams can be tolerated, e.g., if there are fouractuators in the system, up to three jams can be tolerated as there willstill be one actuator left to continue operation. Linear actuator 222,is again utilized among other things, for example, for primary andsecondary flight surface control, similar to that of GRA 22 of the firstembodiment of this invention and includes, as best shown in FIGS. 21 a,21 b, 22 and 25 a, 25 b, unique, special ball nut 226, to be describedin detail hereinafter, that is normally driven by rotatable ball screw224, driven in turn by a schematically illustrated (FIG. 30),bidirectionally rotatable prime mover or main motor 24″, such as aconventional electric motor which may, if necessary, further include aconventional speed reducer gearbox 70″ (again, schematically shown inFIG. 30), with all of the schematically-illustrated items being wellknown in the art and readily commercially available. For ease ofunderstanding, FIGS. 24 a-29 a show the arrangement of the components oflinear actuator 222 in the coupled position, while FIGS. 24 b-29 b showsame in the uncoupled position. The components themselves are the samein the noted two sets of Figures.

As best seen in FIGS. 25-28, it should be understood that thepreviously-noted ball screw 224, having an input gear 230, extendsthrough an axial central aperture 228 of generally-cylindrical ball nut226 and is in operative engagement therewith, so that rotation of theball screw results in axial displacement of the ball nut in theconventional manner. As will be expanded upon later, ball nut 226 isaxially retained in an open-ended, diametrically enlarged, stepped, rearcylindrical portion 234 of a generally cylindrical output rod 232 andsecured against axial movement, relative to output rod 232, via aring-shaped closure member 244 affixed to output rod rear portion 234.Output rod 232 further includes a front portion 236 that terminates intoa clevis-type member 238 having a central aperture 240 adapted for afurther, e.g., pin-type connection. Ball nut 226 is prevented fromrotational movement via two opposite, radially outwardly-directedtrunnions 246, 248 (FIG. 24), fixedly extending from ball nut 226,through corresponding apertures in output rod 232, at an axial portionthereof proximate to closure member 244. Trunnions 246, 248, in additionto serving for the anti-rotation of ball nut 226 and thus output rod232, also permit the axial reciprocation of linear actuator 222 inopposed slots in a conventional peripheral actuator housing (not shown).

Turning now to FIG. 21 a, shown therein is ball screw 224, with inputgear 230, extending through the center of ball nut 226. Ball nut 226, onits outer peripheral surface 252, is provided with preferably threeperipherally equally angularly spaced, axially-extending, raisedportions of generally tooth-like members 254, 256 and 258, each having afront portion “a” axially spaced from a rear portion “b” as well asaxially-spaced, dual-angled, generally rectangular, allochiral (ormirror image) end portions 260, 262, which in turn are axially separatedby laterally abutting, trapezoidal spaces 264, 266 that share a common,short parallel center axial side.

Turning now to FIGS. 21-29, located around ball nut 226, at spaces 264,266, is an annular front locking plate 270 having a smooth peripheralouter surface except for the addition of a radially-extending sectorface gear portion 272, as well as three equally-spaced, radiallyinwardly-extending curved sector portions 274 a, 274 b, 274 c, (FIG. 28)each of which merges, at one end, into an axially-extending toothportion 278 (FIG. 29 a) having a generally trapezoidal shape adapted toengage, in an operative position, with trapezoidal spaces 266 betweentooth-like members 254 a, b; 256 a, b; and 258 a, b, respectively. FIG.23, and particularly FIG. 22, also show a rear locking plate 270′ whichis essentially the same as front locking plate 270, only installed inthe reversed position (or turned around), with like parts thus beingidentified with prime (′) symbols. Rear locking plate 270′, which iscircumferentially slightly offset, relative to front locking plate 270,as best seen in FIGS. 20, and 23, has its tooth portions 278′ (FIGS. 28a, 28 b) adapted to engage with trapezoidal spaces 268 betweentooth-like members 254 a, b; 256 a, b and 258 a, b, respectively.Locking plates 270, 270′ are axially separated from each other, as wellas from output rod 232 and closure member 244, respectively, via three,spaced and interposed radial thrust, rolling element bearings, such asroller bearings 282, as best seen in FIGS. 23 and 27.

Continuing now, particularly with reference to FIGS. 19 and 24-29, adepending flat portion 280 (FIG. 27) of output rod 232 serves as amating and attachment surface for the speed reducer gear box 286 of amode or indexing bidirectional or reversible actuator, such as electricmotor 284, the output member of gear box 286 taking the form of a dualradial face mesh gear 290 having oppositely directed gear face portions292, 292′ that operatively respectively mesh with sector face gearportions 272, 272′ of locking plates 270, 270′. It should be evident, atthis time, that a revolution of mesh gear 290 will, via its oppositeface gear portion engagements with locking plate gear portions 272,272′, cause rotations in opposite directions, of locking plates 270,270′ which, in turn, will cause locking plate foot portions 278, 278′ tomove into and out of engagement, depending upon the direction ofrotation of locking plates 270, 270′, with ball nut tooth portions 254a, 254 b, as well as 256 a, 256 b and 258 a, 258 b and therebyalternately coupling and subsequently decoupling ball nut 226 to outputrod 232.

Briefly turning now to the operation of linear actuator 222, FIGS. 27a-29 a illustrate same during normal operation thereof, i.e., whenoutput rod 232 is mechanically coupled to the grounded housing structure(not shown per se), via the previously-noted intermeshing or coupling ofball nut 226 with the tooth portions 278, 278′ of locking plates 270,270′, respectively. Advancing to FIG. 30, in the coupled or engagedstage/state, main motor 24″, affixed to a non-illustrated groundedhousing portion and acting through a conventional gear box or speedreducer 70″, transfers the rotary motion or torque, via rotatable ballscrew 224, to axially-retained ball nut 226, thus converting the ballscrew's rotary motion to linear, axially reciprocatory movement of theball nut, depending upon the angular direction of rotation of ball screw224. As previously-noted, ball nut 226 can be coupled and uncoupled tooutput rod 232 via disconnect motor 284, gear box 286, face gears 292,292′ and sector gears 272, 272′ of locking plates 270, 270′,respectively. Output rod 232, in turn, is mechanically interconnected(not shown) to the load, i.e., the movable surface that is controlledtherewith.

During such normal operational phases, bidirectional main motor 24″operates to move the noted movable surfaces, as directed, as illustratedin FIG. 30, by a vehicle computer 160″, acting via Command and Powerinputs, through an electronic controller 162″, which in turn controlsthe function of main motor 24″ and, as will be discussed later, alsocontrols the function of disconnect motor 284. A Status input relaysrequired information from controller 162″ back to vehicle computer 160″,with controller 162″ receiving at least some of the following inputsfrom linear actuator 222:

Main Motor Speed from commutator 52″;

Main Motor Current from main motor 24″;

Linear Actuator Output Load (preferably determined by strain) from loadsensor 34″; and

Linear Actuator Output Position (processed, such as by differentiationto determine speed) from position sensor 150″.

Upon the detection of a malfunction, such as, for example of a jam orother failure, of linear actuator 222, as determined by electroniccontroller 162″, based on one or more of the just recited linearactuator inputs, decoupling mechanism 128″ serves to completely severthe load path between linear actuator 222 and the load. Specifically,decoupling mechanism 128″ includes previously-recited face gear 290,driven by reversible/bidirectional disconnect motor 284 via reducergearbox 286, and locking plates 270, 270′. Opposite rotational movementof locking plates 270, 270′, in one direction, causes multipletrapezoidally-shaped tooth portions 278, 278′ to uncouple fromcorresponding trapezoidal spaces 266 between tooth-like members 254 a,b; 256 a, b; and 258 a, b, respectively, which results in completedisengagement of tooth portions 278, 278′ from the correspondingtrapezoidal spaces 260, 262, between the just noted tooth-like members.It remains a first important feature of this invention that the abovedecoupling method or process can, of course, also be reversed, at anytime, (by driving disconnect motor 284 in a reverse or connectdirection) to thereby re-couple the load to linear actuator 222.

In addition, a second important feature of this invention remains thatlinear actuator 222 is provided with sensing device or strain gage 34″to sense or measure, either directly or indirectly, the load present oroccurring at output member or rod structure 232. The system control, asillustrated in FIG. 30, can then compare the input load (either bydirect or indirect measurement, such as via main motor current, and thelike) to the output load, as well as the input speed and the outputspeed (using position and/or velocity sensors at main motor 24″ and theload). This comparison, either by itself or used in conjunction withreadings from additional linear actuators can be used to determine if ajam or other type of failure has occurred within linear actuator 222 orits control.

Since the above-recited two main features, namely the load and speedcomparisons, allow system 220 to offer the same or similar benefits thathave already previously been set forth in the description pertaining tosystem 20 of the first embodiment of this invention they will thus, forthe sake of brevity, not be repeated here. It should also be understoodthat the several actuators and systems of this invention find utility inall types of applications and vehicles in addition to the noted aircraftapplications.

While there are shown and described several preferred embodiments ofthis invention, it is to be distinctly understood that the invention isnot limited thereto, but may be otherwise variously embodied andpracticed within the scope of the following claims.

1. An electromechanical actuator assembly, comprising: an actuator forattachment to a control surface, a load path for transferringcontrol-surface motion to the actuator, a decoupling mechanism forsevering the load path upon detection of a malfunction, a motorproviding decoupling motion, a gear for transferring decoupling motionto the decoupling mechanism wherein, when the gear is rotated in adecoupling direction, the decoupling mechanism severs the load path upondetection of a malfunction.
 2. An electromechanical actuator assembly asset forth in claim 1, wherein the load path comprises a ballscrew and aballnut that moves linearly in response to rotational movement of theballscrew.
 3. An electromechanical actuator assembly as set forth inclaim 2, wherein the ballnut is decoupled from the actuator by thedecoupling mechanism upon detection of the malfunction.
 4. Anelectromechanical actuator assembly as set forth in claim 1, wherein thedecoupling mechanism is a coupling/decoupling mechanism that can alsocouple the load path to transfer control-surface motion to the actuator.5. An electromechanical actuator assembly as set forth in claim 4,wherein the gear is rotated a coupling direction, opposite thedecoupling direction, to couple the load path.
 6. An electromechanicalactuator assembly as set forth in claim 5, wherein the load pathcomprises a ballscrew and a ballnut that moves linearly in response torotational movement of the ballscrew.
 7. An electromechanical actuatorassembly as set forth in claim 6, wherein the ballnut is decoupled fromthe actuator by the decoupling mechanism upon detection of themalfunction.
 8. A method of testing the electromechanical actuatorassembly set forth in claim 7, said method comprising the steps ofrotating the gear in the decoupling direction to confirm decoupling ofdecoupling/coupling mechanism and thereafter driving the gear in thecoupling direction to reestablish the load path for operation.
 9. Incombination, a control surface and a pair of the electromechanicalactuator assemblies set forth in claim 1, wherein both actuators areattached to the control surface whereby, upon decoupling of one loadpath upon detection of the malfunction, the control-surface motion canstill be provided through the other load path.
 10. In combination, acontroller and the electromechanical actuator assembly set forth inclaim 1, wherein the controller controls the rotation of the gear. 11.The combination set forth in claim 10, further comprising a computer,and wherein the controller relays data regarding input-output loads tothe computer, and wherein the computer compares this data to detect amalfunction.
 12. A vehicle comprising a control surface and theelectromechanical actuator assembly set forth in claim 1, wherein thecontrol surface is attached to the actuator and moves in response tocontrol-surface motion transferred through the load path.
 13. A vehicleas set forth in claim 13, wherein the vehicle is an aircraft.
 14. Avehicle as set forth in claim 14, wherein the control surface is aprimary control surface.
 15. A vehicle as set forth in claim 14, whereinthe control surface is a secondary control surface.
 16. A method oftesting the electromechanical actuator assembly in the vehicle set forthin claim 13, said method comprising the steps of driving the gear in thedecoupling direction to confirm decoupling of decoupling/couplingmechanism and thereafter driving the gear in the opposite direction toreestablish the load path for operation.
 17. A method of testing as setforth in claim 16, wherein said steps are performed prior to eachflight.
 18. An aircraft comprising a control surface and a pair of theelectromechanical actuator assemblies set forth in claim 1, wherein thecontrol surface is attached to both actuators, whereby, upon decouplingof one load path upon detection of the malfunction, the control-surfacemotion can still be provided through the other load path.